Two fundamental parameters characterize the technique:                a/ being “opposite” the target;        b/ holding the firearm in a stable way at the moment of departure of the shot.        
In order to master the departure of the shot, the marksman must be able to maintain and control the pressure of his forefinger on the trigger at the nearest possible value to that of the departure of the shot, in such a way as to reach it and to cross the threshold without disturbing the immobility of the firearm. Otherwise, the “finger blow” happens and leads to failure. The tactile sense allows the marksman to evaluate the value of the pressure exercised by the forefinger on the trigger, but not very precisely. The following exercise shows this: if one asks the marksman to compare the trigger of a gun model “DES 69” to that of a revolver model “MR73”, he finds that of the “DES” heavier while the contrary is true (1000 gf against 1360 g, the error being due to the fact that the trigger of the “MR 73” is more progressive).
A good marksman (regional level) presses on the trigger as progressively as possible. He sends the order to his forefinger, then he does not think of it anymore while trying to remain in line. He has to be surprised by the departure of the shot.
An excellent marksman (international level) increases pressure until the threshold of departure of the shot. He maintains this critical pressure until the moment when his sighting line is perfect, and once stabilized, he crosses the threshold without moving his firearm.
A very good marksman (national level) oscillates between the two previous techniques, according to his shape of the moment.